Diffraction optical element and production method therefor

Abstract

In a diffraction optical element having a structure in which a base and an optical adjustment layer adhere to each other, defects such as cracks and peeling occur in the optical adjustment layer, when the adhesive strength between the base and the optical adjustment layer is degraded. In a diffraction optical element 100 of the present invention, a plurality of anchor grooves 3 are formed in a planar second region 6 of a base 1 . Further, a depth of an anchor groove of the plurality of anchor grooves 3 , which is positioned on an outermost side, is designed so as to be smaller than a depth of another anchor groove of the plurality of anchor grooves 3 , which is positioned on an innermost side. An optical adjustment layer 9 adheres so as to cover a first region 5 in which a diffraction grating 2 is formed and the second region 6 in which the anchor grooves 3 are formed of the base 1.

The invention claimed is:  
     
       1. A diffraction optical element, comprising:
 a base made of a first optical material containing a first resin, the base having a diffraction grating shape on a surface thereof; and 
 an optical adjustment layer made of a second optical material containing a second resin, the optical adjustment layer being formed on the diffraction grating shape of the base, 
 wherein the base includes a first region having the diffraction grating shape on a surface thereof, and a second region positioned outside the first region, 
 wherein the optical adjustment layer is formed so as to cover the first region and at least a part of the second region, 
 wherein the second region has a plurality of anchor grooves formed therein, 
 wherein a part of a surface of the second region has a planar shape, and the anchor grooves have a recessed shape with respect to the planar shape, and 
 wherein a depth of an anchor groove of the plurality of anchor grooves, which is positioned on an outermost side, is smaller than a depth of another anchor groove of the plurality of anchor grooves, which is positioned on an innermost side. 
 
     
     
       2. The diffraction optical element according to  claim 1 , wherein, in the plurality of anchor grooves, the anchor groove positioned on the innermost side is deepest, and anchor grooves positioned on an outer side become shallower. 
     
     
       3. The diffraction optical element according to  claim 1 , wherein a depth of a deepest anchor groove of the plurality of anchor grooves is 0.05 mm or less. 
     
     
       4. The diffraction optical element according to  claim 1 , wherein the plurality of anchor grooves each have a concentric shape in which an axis center thereof substantially matches with an axis center of the diffraction grating shape. 
     
     
       5. The diffraction optical element according to  claim 1 , wherein the first region has a convex cross-sectional shape and wherein a cross-sectional shape of a surface of the optical adjustment layer has substantially the same shape as an envelope curve connecting tip ends of diffraction step differences of the diffraction grating shape in the first region and has a substantially planar shape along a shape of the base in the second region. 
     
     
       6. The diffraction optical element according to  claim 1 , wherein the optical adjustment layer has such a thickness that a length from an envelope curve connecting tip ends of diffraction step differences of the diffraction grating shape to a surface of the optical adjustment layer in a normal direction is 0.05 mm or less. 
     
     
       7. The diffraction optical element according to  claim 1 , wherein the first optical material comprises a material having a lower refractive index and higher dispersion as compared with the second optical material. 
     
     
       8. The diffraction optical element according to  claim 1 , wherein the second optical material comprises a composite material containing a resin and inorganic particles. 
     
     
       9. The diffraction optical element according to  claim 8 , wherein the inorganic particles contain, as a main component, at least one kind of oxide selected from the group consisting of zirconium oxide, yttrium oxide, lanthanum oxide, alumina, and silica. 
     
     
       10. The diffraction optical element according to  claim 1 , wherein the first optical material holds a relationship of Expression (2) with respect to the second optical material and a depth d of the diffraction grating in an entire wavelength region to be used; 
       
         
           
             
               
                 
                   
                     
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       11. The diffraction optical element according to  claim 1 , wherein the second region does not have a protruding shape with respect to the planar shape.